Computer Network Assignment A134529
Introduction A fabric of elements that work together much as the fabric or mesh of a net to support the transfer of information. A network includes all links, amplifiers and repeaters, multiplexers, switches, routers, and other intermediate devices involved in establishing, maintaining, and terminating a session between a transmitter and a receiver. Background The first real networks emerged in the nineteenth century. They were telegraph networks dedicated to routing messages around the world. In technical terms they used a primitive form of message switching.. “Voice telephony” was invented, in 1876, by the Scotsman Alexander Graham Bell. This was, and remains, the major breakthrough in telecommunications. The first automatic switching system was invented soon after in 1879. However, initially the telephone networks were based on manual switching by human operators. By the beginning of the 20th century, automatic switching systems began to be widely deployed. These systems were based on electro-mechanically controlled switches, which continued to be the basic switching technology until well into the 1970s. Voice networks are circuit switched networks. A dedicated path (circuit) is established and maintained between the communicating parties for the duration of the call. Data networking is a much more recent innovation. The first modems were invented in the late 1950s. Modems took advantage of the telephone networks of the time, but, by current standards, transmission speeds were a very slow 300 bits/sec (compare that with today’s rates of up to 10 gigabits/sec – that’s 10,000,000,000 bits/sec!). At that time the networks were based on analogue transmission technology and used mechanical switches. Two major developments transformed this networking environment. #Firstly came the digitisation of the major elements of the telephony networks. Digital transmission, based on Pulse Code Modulation (PCM), was complemented by digital switches controlled by simple computers. #Secondly, dedicated switching technology was developed for data communications. Initially two different approaches were adopted for data communications. #Circuit switching networks, based on the same principle as the telephone network, were developed in the late 1970’s. This had limited success. #The alternative approach, “packet switching” has, until now, been the ubiquitous approach to data switching. Packet switching works on the assumption that data is divisible into discrete elements known as packets. Each packet has the address of its destination on the network and is then routed across the network using this address. The distinction between packet and circuit switching is that there is no dedicated physical path maintained across the network in packet switching. The digitisation of networking technology has led to dramatic improvements in the capacities of networks. From the modem capacities of the late 1950s capacities have now risen to the point where individual data streams of 10Gbits/sec are possible. The combination of computerised control for switches and digital transmission technology has led to a new generation of networks that are capable of supporting both voice and data services. This will enable new and advanced services to be delivered. Benefits The benefits of networking (either wired or wireless) in homes are: *'file sharing' : Network file sharing between computers gives you more flexibity than using floppy drives or Zip drives. Not only can you share photos, music files, and documents, you can also use a home network to save copies of all of your important data on a different computer. Backups are one of the most critical yet overlooked tasks in home networking.printer / peripheral sharing - Once a home network is in place, it's easy to then set up all of the computers to share a single printer. No longer will you need to bounce from one system or another just to print out an email message. Other computer peripherals can be shared similarly such as network scanners, Web cams, and CD burners. *'Internet connection sharing' : Using a home network, multiple family members can access the Internet simultaneously without having to pay an ISP for multiple accounts. You will notice the Internet connection slows down when several people share it, but broadband Internet can handle the extra load with little trouble. Sharing dial-up Internet connections works, too. Painfully slow sometimes, you will still appreciate having shared dial-up on those occasions you really need it. *'multi-player games' : Many popular home computer games support LAN mode where friends and family can play together, if they have their computers networked. *'Internet telephone service' : So-called Voice over IP (VoIP) services allow you to make and receive phone calls through your home network across the Internet, saving you money. *'home entertainment' : Newer home entertainment products such as digital video recorders (DVRs) and video game consoles now support either wired or wireless home networking. Having these products integrated into your network enables online Internet gaming, video sharing and other advanced features. Network Classifications Individual networked devices are assigned to appropriate VLANs based on the type of users which have access to them. The possible network classifications are: *Undergraduate Network *Postgraduate Coursework Network *Postgraduate Research Network *Staff Network *Wireless Network *Unregistered Network *Restricted Network *External Network The user categories map to the network categories as follows: *Undergraduate Student, Student Visitors and Guests Undergraduate Network *Honours Student, Postgraduate Coursework Student Postgraduate Coursework Network *Postgraduate Research Student, Staff Visitors and Guests Postgraduate Research Network *Staff Members Staff Network The other network types are for special purposes (regardless of the type of users). The user and network classifications above are based on the level of trust that the Department places in each type of user. It is intended that this policy is one step abstracted from the actual implementation. For example, there can be separate VLANs for Technical, Admin and Academic staff members, but all will have the same access privileges as they will all be classified as Staff Networks. The following lists of allowed and denied traffic will need to be modified once this policy is implemented based on actual results. These lists are a best approximation in the absence of empirical evidence. Types Of Networks Based On Physical Scope One way to categorize the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common examples of area network types are: *LAN - Local Area Network *WLAN - Wireless Local Area Network *WAN - Wide Area Network *MAN - Metropolitan Area Network *SAN - Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network *CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network *PAN - Personal Area Network *DAN - Desk Area Network LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution. Note that these network types are a separate concept from network topologies such as bus, ring and star. LAN - Local Area Network A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet. In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring. WAN - Wide Area Network As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth. A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address. A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances. LAN, WAN and Home Networking Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP) using a broadband modem. The ISP provides a WAN IP address to the modem, and all of the computers on the home network use LAN (so-called private) IP addresses. All computers on the home LAN can communicate directly with each other but must go through a central gateway, typically a broadband router, to reach the ISP. Basic Hardware Components All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In addition, some method of connecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). Less common are microwave links (as in IEEE 802.12) or optical cable ("optical fiber"). Network interface cards A network card, network adapter, or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC addresses. Repeaters A repeater is an electronic device that receives a signal, cleans it of unnecessary noise, regenerates it, and retransmits it at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. Repeaters work on the Physical Layer of the OSI model. Hubs A network hub contains multiple ports. When a packet arrives at one port, it is copied unmodified to all ports of the hub for transmission. The destination address in the frame is not changed to a broadcast address. It works on the Physical Layer of the OSI model.. Bridges A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges broadcast to all ports except the port on which the broadcast was received. However, bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address to that port only. Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived. Bridges come in three basic types: *Local bridges: Directly connect local area networks (LANs) *Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers. *Wireless bridges: Can be used to join LANs or connect remote stations to LANs. Switches A network switch is a device that forwards and filters OSI layer 2 datagrams (chunk of data communication) between ports (connected cables) based on the MAC addresses in the packets. A switch is distinct from a hub in that it only forwards the frames to the ports involved in the communication rather than all ports connected. A switch breaks the collision domain but represents itself as a broadcast domain. Switches make forwarding decisions of frames on the basis of MAC addresses. A switch normally has numerous ports, facilitating a star topology for devices, and cascading additional switches. Some switches are capable of routing based on Layer 3 addressing or additional logical levels; these are called multi-layer switches. The term switch is used loosely in marketing to encompass devices including routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). Routers A router is an internetworking device that forwards packets between networks by processing information found in the datagram or packet (Internet protocol information from Layer 3 of the OSI Model). In many situations, this information is processed in conjunction with the routing table (also known as forwarding table). Routers use routing tables to determine what interface to forward packets (this can include the "null" also known as the "black hole" interface because data can go into it, however, no further processing is done for said data). Conclusion In conclusion, the introduction and the advancement of technology in networking had improve the lifestyle of everyone. With all these networks, we are able to transfer information from one to another either through a wired or wireless network. References Network, The Free Dictionary DANTE (Delivery of Advanced Network Technology to Europe) About.com - Benefits Of Networking http://www.about.com/ http://www.unimelb.edu.au/ http://www.networktutorials.info/index.html Wikipedia